1. Field of the Invention
The present invention relates to a quantum computer using decoherence control and coupling of an atom with an optical resonator.
2. Description of the Related Art
In quantum computers recently well researched, decoherence that destroys a superposition state has come to be a great problem. It is known that decoherence can be suppressed by bang-bang control (see, for example, L. Viola and S. Lloyd, Phys. Rev. A 58, 2733 (1998)). Further, experiments have been reported which proved that bang-bang control enables the coherence time of a nucleic spin of a rare-earth ion in crystal to be extended from 100 ms to 30 s (see, for example, E. Fraval, M. J. Sellars, and J. J. Longdell, Phys. Rev. Lett. 95, 030506 (2005)).
Thus, bang-bang control is effective to suppress decoherence. However, bang-bang control requires repetition of flipping of a state, and hence it is not obvious whether quantum computation can be executed with decoherence suppressed by bang-bang control. In particular, in quantum computers utilizing an optical resonator, the use of bang-bang control has not yet been reported.